Doctorbass said:
is it really 4500mAh out of a 5000mAh after 100 cycles?
That is like 9-10% lost after just 100 cycles!..
do you use them at high C rate? or... maybe tested them at high C-rate?
Yes and no
The 4500 number is not a full discharge cycle (4.20V to 3.0V). It is a more realistic real-life cycle (4.16V to 3.6V). My load of 2 x 12V 50W halogen bulbs in series is not very high so I only discharged at around 4.2A.
Still, I did lose some capacity but I can't say exactly how much because I didn't test the packs when they were new. I also had some weak cells, some puffy ones a even a completely busted one. You can see the discharge curves of all my packs after 100 cycles here: http://endless-sphere.com/forums/viewtopic.php?f=14&t=19145&start=240#p349828
I had to replace some individual cells in some packs and I am completely replacing 4 packs with new ones (they had busted/puffy cells).
All in all I'm really happy about the performance of the cells, but no so much about their durability.
Things I did right:
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-Never charged over 4.16V
-Never discharged under 3.65V (resting voltage)
-Never charged/discharged under 8-10 Celcius or over 30 Celcius
-Never discharged at over 7C (I run 3 x 25C packs in parallel)
-Never charged at over 1C
-Provided good physical protection for the packs, no bouncing around in a bag
Things I did wrong:
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-No cell-level LVC. Eventhough my cells are at 3.65V at resting voltage, some weaker ones might have dropped under 3V on heavy loads at the end of the ride (100A)
-Ran packs with puffy/busted cells in parallel with healthy ones (didn't notice)
-Charged the packs to a full 4.16V every evening after my commute. Left the pack fully charged for the weekend.
Corrective measures:
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-Got some LVC adapters from geoff for next season
-Building a dashboard with multiple cell logs and buzzers to monitor my 24 individual cells while riding.
-Got some clear wrap to be able to inspect my packs for physical damage
-Buying 2 Hyperion 1420i (1100W) so I can charge the entire pack in series in less than an hour in the morning, just before riding instead of the day before). Will never leave the packs in fully charged state for more than an hour.
I will run the same discharge curve tests at the end of next season to see if there was any improvement